<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<body>
		<button class="melon">OK</button>
		
		<script type="text/javascript">
			var btn = document.querySelector("button");
				btn.addEventListener("click",say)
				
					
				
				function say(){     //   添加和移除内存内容必须一致  
					console.log(btn.classList);
					btn.removeEventListener("click",say)   //必须放在这里面    执行完后就移除
				}
		</script>
	</body>
</html>
